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3 years ago

10

What is heat of vaporization?

2 answers:

Sauron [17]3 years ago

8 0

Answer:

D.

Explanation:

The heat of evaporation, is the amount of energy that must be added to a liquid substance, to transform a quantity of that substance into a gas. The heat of vaporization is a function of the pressure at which that transformation takes place.

kirza4 [7]3 years ago

3 0

B. It is the heat required to change a gram of substance from solid to liquid

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You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.8

Lubov Fominskaja [6]

Complete Question

You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.82 when exactly 13 mL of base had been added, you notice that the concentration of the unknown acid was 0.1 M. What is the pKa of your unknown acid?

Answer:

The pK_a value is $pK_a =7.82$

Explanation:

From the question we are told

The volume of base is $V_B = 26.mL = 0.0260L$

The pH of solution is $pH = 7.82$

The concentration of the acid is $C_A = 0.1M$

From the pH we can see that the titration is between a strong base and a weak acid

Let assume that the the volume of acid is $V_A = 18mL= 0.018L$

Generally the concentration of base

$C_B = \frac{C_AV_A}{C_B}$

Substituting value

$C_B = \frac{0.1 * 0.01800}{0.0260}$

$C_B= 0.0692M$

When 13mL of the base is added a buffer is formed

The chemical equation of the reaction is

$HA_{(aq)} + OH^-_{(aq)} --------> A^{+}_{(aq)} + H_2 O_{(l)}$

Now before the reaction the number of mole of base is

$No \ of \ moles[N_B] = C_B * V_B$

Substituting value

$N_B = 0.01300 * 0.0692$

$= 0.0009 \ moles$

Now before the reaction the number of mole of acid is

$No \ of \ moles = C_B * V_B$

Substituting value

$N_A = 0.01800 *0.1$

$= 0.001800 \ moles$

Now after the reaction the number of moles of base is zero i.e has been used up

this mathematically represented as

$N_B ' = N_B - N_B = 0$

The number of moles of acid is

$N_A ' = N_A - N_B$

$= 0.0009\ moles$

The pH of this reaction can be mathematically represented as

$pH = pK_a + log \frac{[base]}{[acid]}$

Substituting values

$7.82 = pK_a +log \frac{0.0009}{0.0009}$

$pK_a =7.82$

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3 years ago

Why do some objects float why others sink

Leona [35]

Because so objects are denser than water and some are less dense than water

4 0

3 years ago

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Arrange the elements in order of increasing atomic size: Li, N, B

alexgriva [62]

Answer:

N, B, Ni

Explanation:

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2 years ago

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g a package of aluminum foil contains 50 ft2 of foil, which weighs approximately 8.0 oz. aluminum has a density of 2.70 g/cm3. w

VMariaS [17]

Answer:

1.8×10^-2mm or 0.018mm

Explanation:

Density = mass/Volume

But volume= area×thickness

Area= 50ft2= 46451.52cm2

Mass=8oz= 226.7962g

Density= 2.70g/cm3

Thickness= mass/density ×area

= 226.7962/46451.52×2.70= 1.8×10-3cm= 1.8×10^-2mm

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3 years ago

Physical or chemical property sugar turns black when heated.

horrorfan [7]

From my understanding the correct answer would be phyical

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3 years ago